[Note (July 2012): I’ve made some minor edits to this blog entry since it was originally posted, cleaning up the text a bit and updating a dead link.]

The UK newspaper "the Sun" is not exactly a bastion of journalistic integrity — it’s a bit like the Weekly World News with a Monty Python accent. So I’m not too surprised that it would have some stupid stories in it, but one they had on their site today really angered me. It’s short, and here it is in its entirety:

AN [sic] asteroid big enough to wipe out mankind is overdue and could strike at any time, scientists fear.

It was thought an impact of the size that wiped out the dinosaurs happened only once in 1/2 million years.

But new evidence studied in Australia suggests a hit equal to 500 Hiroshimas occurs every 1,000 years — and the last was 4,800 years ago.

First off, which scientists? No names, nothing. That’s some journalism!

Next, "wipe out" is way too strong a phrase. An asteroid big enough to kill every human on Earth would have to be roughly 10 kilometers across or bigger, and we have most of those charted (half the near-Earth asteroids bigger than 1 km have already been charted, and 90% is the goal by the end of 2008). Yeah, we’re scared of them — you’d have to be nuts not to be — but we also know that none that big is headed our way in the immediate future.

The really scary ones are the smaller ones — a few hundred meters across — that can come in undetected and kill millions of people if they impact over a city or near a coastline. That would be a disaster of unprecedented proportions for humanity– but it wouldn’t cause an extinction event.

So strike one for The Sun.

Second, it’s not thought that an impact like the dinosaur killer happens every 500,000 years. If that were true, we wouldn’t be here! The last big impact of that size was… when the dinosaurs were wiped out. Duh. The average time between impacts like this is about 200 million years (see page 10 of David Morrison’s paper "Earth Sterilizing Impact"). It’s true that an impact that could destabilize civilization happens every million years or so, but this is different than an extinction-level event.

Strike two.

The last sentence in the article is accurate. I already discussed this before. There is some evidence to suggest we get hit more often than previously thought, but the evidence is scanty. A lot more data are needed.

But what really irritates me is the idea that we are "overdue" for an impact. That’s garbage. Impacts are a stochastic process; they’re random. We could get hit tonight by a big one, or it might be a million years from now. They don’t happen like clockwork, so the impact frequency is a statistical one, like saying how often you get heads when you flip a coin. You have a chance of getting heads every time you flip it, but you cannot say with certainty that you will the next time. And if you flipped tails last time, it doesn’t mean it’ll be heads the next.

The same with asteroids. The idea that we get a big impact every millions years or so doesn’t make asteroids rain down on a schedule.

Asteroid impacts are scary, and there is absolutely no need to make them any scarier by fear mongering like this. Worse, it adds to the "cry wolf" problem that is already plaguing impact scientists — whenever a potentially hazardous asteroid is announced, and sails past us, the public get that much more inured to the real threat from these things (even when scientists are saying the right things). It doesn’t help to have gas thrown on this fire by irresponsible journalism.

The adds for ‘The Sun’ on the telly end with the words “we love it.” which I always find funny or annoying depending on my mood. I tried to read it once but I found that task to be unrewarding.
‘Spitting Image’ on ITV in the ’80s (which was a satirical program with caricature rubber puppets of the famous) portrayed ‘Sun’ journalists as pigs.:)

But what really irritates me is the idea that we are “overdue” for an impact. Thatâ€™s garbage. Impacts are a stochastic process; theyâ€™re random. We could get hit tonight by a big one, or it might be a million years from now. They donâ€™t happen like clockwork, so the impact frequency is a statistical one, like saying how often you get heads when you flip a coin. You have a chance of getting heads every time you flip it, but you cannot say with certainty that you will the next time. And if you flipped tails last time, it doesnâ€™t mean itâ€™ll be heads the next.

The same with asteroids. The idea that we get a big impact every millions years or so doesnâ€™t make asteroids rain down on a schedule.

Unless, of course, you buy into the Nemesis hypothesis, or one of the other similar conjectures that in fact does result in periodic impacts. The catch here, though, is that according to this model we’re about midway between impacts (if memory serves), so “overdue” is still incorrect.

Having grown up in England I learned long ago to take absolutely everything in The Sun with a very large pinch of salt, but this highlights a trend in journalism which I’m noticing more and more often – not just in England but also in Australia, since I moved here a couple of years ago.

Basically, speculation by scientists or some other “authority figure” – could be lawyers, doctors, etc – talking about a theoretical set of circumstances is reported as news, on the basis that it might happen and there we should be worried about it. And more often than not I suspect the “journalist” who writes this “news” has actually had a conversation like this with some random “authority figure”:

Journalist: Theoretically an asteroid big enough to kill a lot of the living things on Earth crashes into the Earth every few million years, doesn’t it?
Scientist: Well yes, theoretically, in the past, that sort of event has happened every few million years or so.
Journalist: And it has been a lot longer than a few million years since the last time it happened, hasn’t it?
Scientist: Well, um, yes it has, but you see, the thing is…
Journalist: Great, thanks!

And the journalist goes away and writes the sort of rubbish this article is about!

It’s just a plot by the clergy of various religions to make scientists look bad. Wink, Wink!!!

Still, as scientists become more and more authotitative and the subjects with which we deal more esoteric, those who do understand them must be either held in near religious awe, or demeaned as idiots and crooks, depending on the audience.

Ahhh, the trials and tribulations of being right (most of the time).

I still remember my ex-wifes bumper sticker:
People who think they know it all, really piss off those of us who do,,,

,,,and on the flip side:
People who SEEM to know it all, really piss off everybody,,,

I’ve been curious about the probabliltiy estimates. It would seem to me that the probabilities should be lower than the historical incidence because so many objects have already been captured by Jupiter, Saturn, Earth, etc. And the creation events are presumably not happening any more, since the solar system doesn’t contain high density gas. Am I missing something?

Ah, satire, thy name is Mo-Man. Hi ya k’Allah (ok, it’s probably really bad phonetic spelling, but it’s the best I can do).

A few definitions:
Evil: Those actions which are not conducive to the common good.
Stupidity: Those actions which lead to evil.

We are a social species which evolved because our actions aid in our survival as a species. That is the good. That is intelligent. Environment changes and, because some few of us HAPPEN to have the right qualities to survive in the new environment, continue to propagate. Thus the species evolves into a more intelligent, loving, kind and good(sic) species. Some envitonmental changes may occur too rapidly for ANY individuals to survive. That is extinction.
I hope we will spread so far and wide, that no such environmental challenge can ever wipe out all of our species. Go, space colonization. It’s one way to create more land for the dispossesed, such as Palistinians. Just build a new country in space,,,but what are the odds?

At the risk of massive ad hominem sniping, I am reminded of the IAU definition of a planet:

[i]A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.[/i]

Now, item “c” is the interesting one here. Certainly, we are still charting the various rocks, asteroids, and other items in our solar system, and we are not even certain that we know about all of them. However, if, because it is a planet, and presuming that there is a modicum of accuracry in this definition, the earth has cleared out “its neighborhood”, then over the aeons of time, shouldn’t the probability of an asteroid strike be diminishing?

If the Sun really is on level with the Weekly World News, then people will pretty much recognize it as self-parody. In that case, what you should be annoyed about is trivial treatment of a real, if oft-exagerated, problem.

Now, item â€œcâ€ is the interesting one here. Certainly, we are still charting the various rocks, asteroids, and other items in our solar system, and we are not even certain that we know about all of them. However, if, because it is a planet, and presuming that there is a modicum of accuracry in this definition, the earth has cleared out â€œits neighborhoodâ€, then over the aeons of time, shouldnâ€™t the probability of an asteroid strike be diminishing?

First of all, you’re right that it should be diminishing, but it will be extremely gradual. We do decrease the chances of future hits as time goes on, but only when one actually hits us.

Now, onto the “cleared its neighborhood” bit. What I believe this means is that it’s cleared off asteroids that share a very similar orbit to it (excluding Trojans). Even with this done, there’s still the possibility of there being many asteroids that have orbits which intersect Earth’s at one of two points (which we term “Meteoroids”), and these are the ones we have to worry about.

Unfortunately there are a good number of people who read tabloid papers not for fun, but they think there is a great deal of truth to be told in them.

Regarding the whole statistical thing of it all. There are far too many people who just cannot seem to grasp simple statistical concepts. You have no idea how many times I have gotten into arguments with someone who thinks that if they flip a coin twice and it lands tails the first time they are more likely to get heads the second time. Maybe my way of explaining it is bad, but it usually takes me a great deal of time before the person goes “ohh… but what about lottery tickets? If I lose this week I am more likely to win next week, right?”. That is when I just give up.

You know my friends read articals like this all the time, knowing how much I love space, they come screaming at me in a horrific exitment. I just wince at them and say those “scientists” can jump off a cliff.

I would agree with the smaller astriods, they’re the sneaky ones that like to take down pray silently. At least if one hits near a coast I won’t be done for.

My friend the other day came yapping to me about an astriod that was over-due to hit Earth, and will definatly hit it by 2012. Strangly enough that’s when the Mayan calander ends and that’s the year that doomsdayers claim the world will end. I’ve also noticed how NASA is sitting on their hands on this one.

Well I never listen to journalists, all they know is persuasive talking. They’re not scientists or psychologist, they just repeat what other fat donut loving people tell them to say. I would like for some news without the automotanic element in them. -_-‘

Jason B ; I think it was Dr. Jerry Pournell who did some calculations in that regard some years ago. Meteors heat up due to compression of the earths atmosphere, slowing dwon due to their cross section vs mass, but he came to an approximate mass of 50,000 tons as being massive enough to not be slowed significantly by the atmosphere. At 30 km per second, from first visible heating effects(ie, when it becomes visibly hot) to the surface impact would thus take about 5 to 7 seconds, assuming a straight down impact. In 1973, a pretty large one grazed the earths upper atmosphere and I heard it stated that IF it had touched down it would have had a Tungusga yield (or a few dozen kilo tons). Of course, my memories are not perfect and those estimates are from the visible track it created but that would still be some big fireworks effect. Anything much less massive than 50,000 tons would be slowed so much it would not have fission bomb equivelance but could sure play havoc with some ones house,,,

The “overdue” statistical conclusion reminds me of the question: If I flip a coin 30 times and it lands on heads every time, what are the odds on the 31st flip? Statisticians say 50-50. That’s wrong. If I got heads 30 times in a row, then I was almost certainly cheating and number 31 will probably be heads.

What does this have to do with global annihilation? Just about as much as the Sun article.

When most media reports an earthquake an explanation of the Richter scale isn’t far behind, especially since I suspect the majority are ignorant of logarithmic scales. When an article is published about an asteroid impact, and indeed many are legit, an explanation of the Torino scale should be included. Math can clarify things because “how much?” in science is like the queen on the chess board. You can win without it but she sure helps immensely. The article wasn’t total poppycock like you’d get with an alien abduction fabricated story, instead it appears to me to be shoddy reporting being distorted through a vulgar lens. I see it all the time. Journalists don’t usually have scientific credentials! I’d also like to see disclaimers after astrology columns.

A few years ago I was on a technical writing course, and learned of something called the Gunning-Fogg (sp?) Index. This is a means of calculating (approximately) the number of years of continuous education required to understand a piece of writing. The tutor used, as an example, an article from The Sun. This article had a Gunning-Fogg Index of 3 (so would be expected to be understood by a 7-year-old child).

I wish an asteroid would smack into one of the rocky bodies of the solar system, preferably one close to Earth (but not Earth itself – that would be a huge inconvenience and would disrupt my important schedule of being a lazy bum). Seeing Jupiter take some lumps was cool, but we didn’t get to see lasting impact formations, and there’s little left of the impacts that we can actually study (if there’s anything left at all). I want to see Mercury or Venus get the snot knocked out of it by a 10-mile (22 kilometer if you’re sciency) wide monster. Having one that size hit Mars would be even cooler because hey, we’ve got stuff on the planet and orbiting it that could record the effects! Unfortunately, I’ll probably be dead and my carbon atoms recycled through the Earth’s mantle several times over before THAT happens. Poo.

I would suggest you did some research before judging the Sun’s / tabloid newspaper’s report. It would appear the article is actually based on some serious scientific research, reported in the New York Times (also available on-line). This is an extract :

At the southern end of Madagascar lie four enormous wedge-shaped sediment deposits, called chevrons, that are composed of material from the ocean floor. Each covers twice the area of Manhattan with sediment as deep as the Chrysler Building is high.
On close inspection, the chevron deposits contain deep ocean microfossils that are fused with a medley of metals typically formed by cosmic impacts. And all of them point in the same direction â€” toward the middle of the Indian Ocean where a newly discovered crater, 18 miles in diameter, lies 12,500 feet below the surface.
The explanation is obvious to some scientists. A large asteroid or comet, the kind that could kill a quarter of the worldâ€™s population, smashed into the Indian Ocean 4,800 years ago, producing a tsunami at least 600 feet high, about 13 times as big as the one that inundated Indonesia nearly two years ago. The wave carried the huge deposits of sediment to land.
Most astronomers doubt that any large comets or asteroids have crashed into the Earth in the last 10,000 years. But the self-described â€œband of misfitsâ€ that make up the two-year-old Holocene Impact Working Group say that astronomers simply have not known how or where to look for evidence of such impacts along the worldâ€™s shorelines and in the deep ocean.
Scientists in the working group say the evidence for such impacts during the last 10,000 years, known as the Holocene epoch, is strong enough to overturn current estimates of how often the Earth suffers a violent impact on the order of a 10-megaton explosion. Instead of once in 500,000 to one million years, as astronomers now calculate, catastrophic impacts could happen every 1,000 years.
The researchers, who formed the working group after finding one another through an international conference, are based in the United States, Australia, Russia, France and Ireland. They are established experts in geology, geophysics, geomorphology, tsunamis, tree rings, soil science and archaeology, including the structural analysis of myth. Their efforts are just getting under way, but they will present some of their work at the American Geophysical Union meeting in December in San Francisco.
This year the group started using Google Earth, a free source of satellite images, to search around the globe for chevrons, which they interpret as evidence of past giant tsunamis. Scores of such sites have turned up in Australia, Africa, Europe and the United States, including the Hudson River Valley and Long Island.
When the chevrons all point in the same direction to open water, Dallas Abbott, an adjunct research scientist at Lamont-Doherty Earth Observatory in Palisades, N.Y., uses a different satellite technology to look for oceanic craters. With increasing frequency, she finds them, including an especially large one dating back 4,800 years.
So far, astronomers are skeptical but are willing to look at the evidence, said David Morrison, a leading authority on asteroids and comets at the NASA Ames Research Center in Mountain View, Calif. Surveys show that as many as 185 large asteroids or comets hit the Earth in the far distant past, although most of the craters are on land. No one has spent much time looking for craters in the deep ocean, Dr. Morrison said, assuming young ones donâ€™t exist and that old ones would be filled with sediment.
Astronomers monitor every small space object with an orbit close to the Earth. â€œWe know whatâ€™s out there, when they return, how close they come,â€ Dr. Morrison said. Given their observations, â€œthere is no reason to think we have had major hits in the last 10,000 years,â€ he continued, adding, â€œBut if Dallas is right and they find 10 such events, weâ€™ll have a real contradiction on our hands.â€
Peter Bobrowsky, a senior research scientist in natural hazards at the Geological Survey of Canada, said â€œchevrons are fantastic featuresâ€ but do not prove that megatsunamis are real. There are other interpretations for how chevrons are formed, including erosion and glaciation. Dr. Bobrowsky said. It is up to the working group to prove its claims, he said.
William Ryan, a marine geologist at the Lamont Observatory, compared Dr. Abbottâ€™s work to that of other pioneering scientists who had to change the way their colleagues thought about a subject.
â€œMany of us think Dallas is really onto something,â€ Dr. Ryan said. â€œShe is building a story just like Walter Alvarez did.â€ Dr. Alvarez, a professor of earth and planetary sciences at the University of California, Berkeley, spent a decade convincing skeptics that a giant asteroid wiped out the dinosaurs 65 million years ago.
Ted Bryant, a geomorphologist at the University of Wollongong in New South Wales, Australia, was the first person to recognize the palm prints of mega-tsunamis. Large tsunamis of 30 feet or more are caused by volcanoes, earthquakes and submarine
Deposits from mega-tsunamis contain unusual rocks with marine oyster shells, which cannot be explained by wind erosion, storm waves, volcanoes or other natural processes, Dr. Bryant said.
â€œWeâ€™re not talking about any tsunami youâ€™re ever seen,â€ Dr. Bryant said. â€œAceh was a dimple. No tsunami in the modern world could have made these features. End-of-the-world movies do not capture the size of these waves. Submarine landslides can cause major tsunamis, but they are localized. These are deposited along whole coastlines.â€
For example, Dr. Bryant identified two chevrons found over four miles inland near Carpentaria in north central Australia. Both point north. When Dr. Abbott visited a year ago, he asked her to find the craters.
To locate craters, Dr. Abbott uses sea surface altimetry data. Satellites scan the ocean surface and log the exact height of it. Underwater mountain ranges, trenches and holes in the ground disturb the Earthâ€™s gravitational field, causing sea surface heights to vary by fractions of an inch. Within 24 hours of searching the shallow water north of the two chevrons, Dr. Abbott found two craters.
Not all depressions in the ocean are impact craters, Dr. Abbott said. They can be sink holes, faults or remnant volcanoes. A check is needed. So she obtained samples from deep sea sediment cores taken in the area by the Australian Geological Survey.
The cores contain melted rocks and magnetic spheres with fractures and textures characteristic of a cosmic impact. â€œThe rock was pulverized, like it was hit with a hammer,â€ Dr. Abbott said. â€œWe found diatoms fused to tektites,â€ a glassy substance formed by meteors. The molten glass and shattered rocks could not be produced by anything other than an impact, she said.
â€œWe think these two craters are 1,200 years old,â€ Dr. Abbott said. The chevrons are well preserved and date to about the same time.
Dr. Abbott and her colleagues have located chevrons in the Caribbean, Scotland, Vietnam and North Korea, and several in the North Sea.
Hither Hills State Park on Long Island has a chevron whose front edge points to a crater in Long Island Sound, Dr. Abbott said. There is another, very faint chevron in Connecticut, and it points in a different direction.
Marie-AgnÃ¨s Courty, a soil scientist at the European Center for Prehistoric Research in Tautavel, France, is studying the worldwide distribution of cosmogenic particles from what she suspects was a major impact 4,800 years ago.
But Madagascar provides the smoking gun for geologically recent impacts. In August, Dr. Abbott, Dr. Bryant and Slava Gusiakov, from the Novosibirsk Tsunami Laboratory in Russia, visited the four huge chevrons to scoop up samples.
Last month, Dee Breger, director of microscopy at Drexel University in Philadelphia, looked at the samples under a scanning electron microscope and found benthic foraminifera, tiny fossils from the ocean floor, sprinkled throughout. Her close-ups revealed splashes of iron, nickel and chrome fused to the fossils.
When a chondritic meteor, the most common kind, vaporizes upon impact in the ocean, those three metals are formed in the same relative proportions as seen in the microfossils, Dr. Abbott said.
Ms. Breger said the microfossils appear to have melded with the condensing metals as both were lofted up out of the sea and carried long distances.
About 900 miles southeast from the Madagascar chevrons, in deep ocean, is Burckle crater, which Dr. Abbott discovered last year. Although its sediments have not been directly sampled, cores from the area contain high levels of nickel and magnetic components associated with impact ejecta.
Burckle crater has not been dated, but Dr. Abbott estimates that it is 4,500 to 5,000 years old.
It would be a great help to the cause if the National Science Foundation sent a ship equipped with modern acoustic equipment to take a closer look at Burckle, Dr. Ryan said. â€œIf it had clear impact features, the nonbelievers would believe,â€ he said.
But they might have more trouble believing one of the scientists, Bruce Masse, an environmental archaeologist at the Los Alamos National Laboratory in New Mexico. He thinks he can say precisely when the comet fell: on the morning of May 10, 2807 B.C.
Dr. Masse analyzed 175 flood myths from around the world, and tried to relate them to known and accurately dated natural events like solar eclipses and volcanic eruptions. Among other evidence, he said, 14 flood myths specifically mention a full solar eclipse, which could have been the one that occurred in May 2807 B.C.
Half the myths talk of a torrential downpour, Dr. Masse said. A third talk of a tsunami. Worldwide they describe hurricane force winds and darkness during the storm. All of these could come from a mega-tsunami.
Of course, extraordinary claims require extraordinary proof, Dr. Masse said, â€œand weâ€™re not there yet.â€
Correction: Nov. 16, 2006
An article in Science Times on Tuesday about new research suggesting that a comet or an asteroid may have struck the Indian Ocean 4,800 years ago included an incorrect estimate from researchers for the frequency of such collisions. The current estimate is one impact on the order of a 10-megaton bomb every 1,000 years, not every few thousand years. The article also misstated the name of a state park on Long Island that has a large sand wedge called a chevron, which may indicate that a comet or meteor landed in the ocean nearby. It is Hither Hills, not Heather Hill.
Correction: Dec. 1, 2006
An article in Science Times on Nov. 14 about new research suggesting that a comet or an asteroid may have struck the Indian Ocean 4,800 years ago misspelled the name of a scientist at the Geological Survey of Canada who specializes in natural hazards. He is Peter Bobrowsky, not Bobrowski.

2. You apparently haven’t read this blog before. Or payed much attention to what Phil actually wrote. He previously mentioned the very article you pasted and the possibility of those results. His article above includes a link to his previous blog entry on that topic.

3. The issue is not about whether asteroids/comets have impacted Earth, or how frequently on average it occurs. The real complaint is against the mistaken impression given by the word “overdue”. Overdue implies that there is a regular, clocklike pattern of impacts. It implies that there is a schedule. This is erroneous. Random impacts are random. The best we could say would be that no impacts have occurred in far longer time than any known gap in history. That’s not quite the same thing as saing that an impact will occur tomorrow.

You fellows should read Cosmic Winter by Victor Clube and Bill Napier, two distiguished british astronomers. They contend, with significant evidence, that the distribution of astreroids and comets is anything but random through time and orbits, and that they display significant periocidity.

The placement of rocks in our path is not governed by “random flips of coins” but by the periodic disintegration of larger body comets which leave material bunched into discreet orbital groups.

When we see the Taurids in June we are not seeing the coin show up “heads” many times each June, we are seeing a non-random event. And sometimes it is real heavy.

# we also know that none [of the asteroids] that big [10km]
# are headed our way in the immediate future.

No, unfortunately we don’t. The southern hemisphere is mostly unmonitored, so any asteroid coming from that direction would likely be undetected — as would an asteroid coming from the direction of the Sun, due to solar glare. The reality of the situation today remains largely as David Morrison (NASA) described in September 1998: “With so many of even the larger NEOs remaining undiscovered, the most likely warning today would be zero — the first indication of a collision would be the flash of light and the shaking of the ground as it hit.”